Closer examination, however, confirmed that a polar shark had ventured into tropical regions. Its characteristic head and the size and shape of its fins made its identification possible.

Led by Kidd Carrig, 16, a team that annually participates in Polar Plunge Chicago has grown to over 100 people, raising over ...

Measuring the Greenland shark’s growth rate is challenging because individuals are rarely recaptured. However, one shark tagged in 1936 had only grown 2.3 inches when it reappeared 16 years later.